Each subject will undergo Screening (Day -28 to Day -2). Subjects will return to the clinical site on Day -1, be admitted to the unit, and eligibility will be reconfirmed. Eligible subjects will receive a single dose of investigational medicinal product (IMP, NSI-189 Phosphate or Placebo) on Day 1 and will be followed for safety and PK until discharge on Day 3. Subjects who are experiencing any significant AEs that are considered possibly related to study drug will be kept at the unit for an additional day (or longer) until the event resolves or it is considered medically safe for the subject to be discharged. Subjects will have a telephone Follow-up on Day 4 and return to the unit on Day 7 (± 1) for End-of-study. Participation of an individual subject may last up to 36 days from the time of Screening until the End-of-study.